Install from binary and allow "stable" version

Hi,

This PR mainly introduces 2 new features:
- The ability to use "stable" as version number. The highest stable version is retrieve through a new facter that parse the http://nodejs.org/dist/ like done by [n](https://github.com/visionmedia/n) or [nave](https://github.com/isaacs/nave)
- The ability to install node from pre-built versions available at http://nodejs.org/dist/ like intended by @colinmutter in [this fork](https://github.com/colinmutter/puppet-nodejs) but without duplicating code.

This PR also fixes an issue with `install.sh` that requires `curl`.

Breaking changes:
- The node binary is no longer suffixed with the version number in `/usr/local/bin/` to ensure that the `node` binary is always the right one under `/usr/local/bin/node`.

I haven't been able to update all the specs because my ruby environment is broken, really sorry 'bout that.
Nevertheless I have heavily tested it through Vagrant (install node from a built distribution, reinstall the same version twice, compile a version, install a previous version, and so on).

Hope you like this PR.

Cheers,
Antoine